Sciences des matériaux

Nombre total de résultats : 419
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EFFET DU TRAITEMENT THERMIQUE SUR LE COMPORTEMENT CORROSIF DU TI-6AL-4V DANS DES MILIEUX ACIDES

S.LEBOUKH*, A.ZIOUCHE, T. KACEL, A.FEGHOUL  (2014)
Article de conférence

Le titane et ses alliages sont largement utilisés, en raison de leurs propriétés intéressantes, en particulier leur excellente résistante à la corrosion combinée à des propriétés mécaniques élevées. De fait, ce sont des matériaux qui trouvent de larges applications dans les domaines aéronautique, spatial et biomédicale ainsi que dans l'industrie automobile, spécialement l'alliage Ti6Al4V.Ce travail est focalisé sur l’étude des performances physico-chimique d'alliages de titane biphasé α+β (Ti-6Al-4V) après un traitement thermiques et sur la nature des produits de corrosion après essai d’immersion dans des milieux acides. Les microstructures obtenues ont été observées par microscope optique ainsi que des mesures de la microdureté HV afin d’estimer les modifications apportées. L’objectif de notre travail est d’étudier la caractérisation de la corrosion d’un alliage dont la composition Ti-6Al-4V, pour cela on a étudié les caractéristiques métallurgiques des échantillons avant et après le traitement thermique. Voir les détails

Mots clés : Ti6Al4V, traitement thermique, milieu acide, produits de corrosion.

Sparse Representations of Acoustic Emission Signal:Application to Damage Analysis in Glass Fiber Reinforced Composites

Abida Satour, Silvio MONTRESOR, Mourad Bentahar, Rachid El GUERJOUMA, Fouad Boubenider  (2013)
Article de conférence

Sparse representation of signals has been subject of many advances during recent years especially in the field ofapplied physics. The problem is to search for the most compact representation of signals in terms of linearcombinations of elementary waveforms in an over-complete dictionary. The underlying hypothesis in most ofsparse representation problems is that if one can associate a sparse representation to a given signal, its structurereveals information directly linked to the physical nature of the addressed problem. From this point of view it hasbeen shown that sparse representation problems have closed connexions with inverse problems and sourceseparation problems. In this contribution, an application of sparse representation techniques to identify damagemechanisms from Acoustic Emission (AE) signals is presented. The sparse representation is which is based onthe continues wavelet transform. All experiments concern investigations realized on glass fibre reinforcedpolymer composites (GFRP). Voir les détails

Mots clés : acoustic emission, Signal processing, Ultrasonic, precursor damage

New approach for the damage mechanisms identification in the glass-epoxy composites

A.Satour, S.Montrésor, M.Bentaharb, F.Boubeniderc and R. Elguerjouma  (2012)
Article de conférence

The aim of this work is to introduce a new approach for clustering acoustic emission data occuring during the fracture process of glass fibre reinforced polymer (GFRP) plates. In particular, we have developed signal processing techniques based on continues wavelet transform (CWT) in order to isolate acoustic signature corresponding to each damage mechanism (fibre breakage, matrix cracking, etc.). Entropy criterion was used to provide selection of most significant wavelet coefficients of AE signals. Models are established in the form of dictionaries, whose elements are the waveforms collected during specific experiments in which the created damage mechanisms are well known. Dictionaries should be used to classify acoustic emission signals recorded when polymer composites are under load. Voir les détails

Mots clés : acoustic emission, wavelet transforme, damage mechanisms

Photolithographic processes for achievement miniature piezoelectric devices IDT

SAFOU Abdelkader, BADIDI BOUDA Ali, ZERDALI Mokhtar, HAMZAOUI Saad  (2014)
Article de conférence

This paper deals transducer with the technology of piezoelectric IDTs (Interdigital transducers) by photolithographic technique, especially SAW (Surface Acoustic Waves) sensors. We conducted synthesis of thin layers of zinc oxide doped copper on glass substrates Corning glass, using Radio Frequency RF technology, then we elaborate interdigitated fingers IDT miniatures on glass substrates, silicon and quartz. Finally, a microlocation of ZnO piezoelectric on the IDT.We proceeded to the achievement of interdigitated fingers IDT, through microlithography technical, and deposition of layers of ZnO:Cu on IDT by sputtering RF technical. For this, we developed the insulation technique by projection mode optics. The main purpose of this technique is the miniaturization of devices IDT. Characterization techniques were implemented for characterizing of ZnO layers, such as the X-ray diffraction, the scanning electron microscopy MEB and optical microscopy for IDT devices. The minimum reduction is obtained of 1/ 30; this has yielded IDT for width and spacing of 5 microns. This technique has also improved the miniaturization factor an order of 30. Voir les détails

Mots clés : SAW sensor, fingers interdigitated IDT, Photolithography, Piezoelectricity, RF sputtering

Un algorithme de seuillage doux modifié pour la transformée en ondelettes: Application au débruitage de signaux d’émission acoustique

Abida Satour, Silvio Montrésor, Mourad Bentahar, Rachid El GUERJOUMA, Fouad Boubenider  (2013)
Article de conférence

Nous présentons une méthode de débruitage par transformée en ondelettes de signaux d’émission acoustique (EA) utilisés pour la caractérisation des processus d’endommagements de matériaux composites sous contraintes mécaniques. L’objectif est d’améliorer la sensibilité de la chaine de traitement afin de pourvoir prendre en compte les signaux d’EA de très faible amplitude, condérérés comme précurseurs, qui apparaissent au début des tests de contrainte menant à la rupture du matériaux. Voir les détails

Mots clés : Transformée en ondelettes, Emission acoustique, débruitage

La simulation et étude de la corrosion de la ZATM du procédé FSW d’alliaged’Aluminium 6082 T651

a.labed, A.ZIOUCHE, m.aissani, B.Idir  (2014)
Article de conférence

Ce travail est un plus à l'étude de la soudabilité de l'aluminium par le procédé FSW. Il présente les microstructures obtenues après la simulation de la zone affecté thermomécaniquement de la soudure dans un équipement de simulation spécifique. Des observations métallographiques et des mesures de microduretés sont employées comme techniques de caractérisation et ainsi des essais de corrosion. Voir les détails

Mots clés : 6085T651, FSW, ZATM, corrosion

Study of the morphological and optical properties of transparent electrodes based on indium tin oxide (ITO) for photovoltaic applications

S.MAHDID, Y.Benmadani  (2014)
Article de conférence

Metal oxides are materials which may have the dual property of having a high electrical conductivity and good transparency in the visible range. They are called "transparent conductive oxides" TCO. The indium oxide ITO (indium tin oxide) is usually used as a transparent electrode as for the third generation solar cells.This work is devoted to the realization and characterization of transparent electrodes based on thin films of indium oxide doped with tin (ITO), which are deposited on a glass substrate by the method of spin-coting. After chemical treatment in specific locations we performed different characterizations.Optical characterization of transparent electrodes developed allowed us to deduce the various optical parameters such as transmission (170-2100 nm), the energy gap and extinction coefficient as a function of the thickness and the spectroscopic determination the refractive index n thanks to ellipsometry measurements. The AFM measurements characterize the surface topology of material and provide information in particular on the surface roughness and the grain size of the material studied. These measurements are performed using an atomic force microscope mode functioning contactThe obtained results on the preparation and characterization of transparent electrodes based on indium oxide ITO, shows that the ITO thin film has good transparency to visible light and also exhibits good conductivity thereby used as the transparent electrodes Voir les détails

Mots clés : transparent electrodes, ITO, thin film

The effect of successive repairs on the weldment quality of API 5L X-70 pipeline steel H.S.L.A

B.MAAMACHE, M.BOUABDALLAH, H.BRAHIMI, Y.YAHMI, B.MEHDI  (2014)
Article de conférence

The effect of successive repairs on the weldment quality of API 5L X-70 pipeline steel H.S.L.A Voir les détails

Mots clés : welding, Heat affected zone, Thermal cycles, DRX, HSLA

   Mechanical properties and characterization of metallic bond coat used in hardfacing of   petroleum drill bits

Youcef YAHMI, Djamel Miroud, Bouzid MAAMACHE, Ridha BADI  (2014)
Article de conférence

     Tungsten carbides are widely used as weld hardfacing deposits in petroleum drill bits. To assure proper bonding of the hardfacing to the substrate, several choices of bond coating layers are offered. In this study, tow different commercial powders A and B and mixtures of both them were thermal sprayed onto a carbon steel XC18 substrate used in petroleum drill bits. The micro hardness respectively, of the hardfacing surface and bond coating layers was measured. The microstructure was observed by optical microscopy and field emission scanning electron microscope equipped with energy-dispersive X-ray spectrometry.      It has been observed that the mixture of 75% of A and 25% of B produces an uniform coating metallurgically bonded to the substrate with a little heat affected zone and a little amount of porosity. Voir les détails

Mots clés : Thermal spray coating, drill bit, Bond coat layer, weld hardfacing, adhesion.

Microstructural and mechanical characterization of dissimilar weldedjoint between 2205 duplex stainless steel and API X52 HSLA steel

B. BELKESSA, D. Miroud, N. OUALI, Y. YAHMI  (2014)
Article de conférence

In this work we study the evolution of the microstructure and phase transformations along the welded joint and the mechanical properties of dissimilar metals weld between duplex stainless steel and HSLA steel. Welds are produced by shielded metal arc welding (SMAW) using a duplex grade filler metal (E2209). The welds obtained in this study, have good mechanical properties, despite the appearance of a hard zone at the interface between the weld metal and the heat affected zone of the HSLA steel Voir les détails

Mots clés : duplex stainless steel, API 5L X52, Dissimilar welding, Heat affected zone